Field of the Disclosure
The present disclosure generally relates to controlling lost circulation in a wellbore during drilling with a drilling fluid. More specifically, embodiments of the disclosure relate to a lost circulation material (LCM).
Description of the Related Art
Lost circulation is one of the frequent challenges encountered during drilling operations. Lost circulation can be encountered during any stage of operations and occurs when drilling fluid (or drilling mud) pumped into a well returns partially or does not return to the surface. While some fluid loss is expected, excessive fluid loss is not desirable from a safety, an economical, or an environmental point of view. Lost circulation is associated with problems with well control, borehole instability, pipe sticking, unsuccessful production tests, poor hydrocarbon production after well completion, and formation damage due to plugging of pores and pore throats by mud particles. Lost circulation problems may also contribute to non-productive time (NPT) for a drilling operation. In extreme cases, lost circulation problems may force abandonment of a well.
Lost circulation can occur in various formations, such as naturally fractured formations, cavernous formations, and high permeable formations. Lost circulation can be categorized by the amount of fluid or mud lost as seepage type, moderate type, severe type, and total loss. The extent of the fluid loss and the ability to control the lost circulation with an LCM depends on the type of formation in which the lost circulation occurs. Seepage type and moderate type lost circulation may occur in high permeable formations, extremely high permeable formations (“referred to as “super-K” formations), and fissured and fractured formations. In addition to the natural causes of lost circulation, subsurface formations having a narrow mud weight window, such as weak and unconsolidated formations, depleted formations, and high pressure zone formations, may also cause moderate type to severe type lost circulation due to the creation of induced fractures in the near wellbore formation. Such lost circulation may occur when the mud weight used for well control and borehole stability exceeds the fracture gradient of the formation.